1. Field of the Invention
The present invention relates to a sensing method and a sensing system. More specifically, the invention relates to a sensing method utilizing circularly polarized light and a sensing system.
2. Description of the Related Art
A method utilizing polarized light is known in the related art as a sensing method. In JP2008-58270A, for example, cracks on a silicon substrate are sensed with a system of irradiating the silicon substrate with polarized infrared light through a first linear polarizing filter and receiving reflected light or transmitted light from the silicon substrate through a second linear polarizing filter. This technology is acquired by using a phenomenon that the light intensity which can be sensed decreases, in a case where the reflected light or transmitted light of a portion without cracks is linearly polarized light and travels through the second linear polarizing filter, except for a case where specific conditions are satisfied, however, light which can be sensed is generated even in a case where the reflected light or transmitted light on the portion with cracks travels through the second linear polarizing filter due to diffuse reflection. In JP2013-36888A, a technology utilizing circularly polarized light in the technology of JP2008-58270A is disclosed.
WO 2014/181799 discloses a system of detecting foreign materials on a specular reflector, a transparent film, or a person as a target object, by using a film including a near infrared circularly polarized light separation layer and a visible light shielding layer.